On the contribution of overt tactile expectations to visuo-tactile interactions within the peripersonal space.

Since the discovery of neural regions in the monkey brain that respond preferentially to multisensory stimuli presented in proximal space, researchers have been studying this specialised spatial representation in humans. It has been demonstrated that approaching auditory or visual stimuli modulate tactile processing, while they are within the peripersonal space (PPS). The aim of the current study is to investigate the additional effects of tactile expectation on the PPS-related multisensory interactions. Based on the output of a computational simulation, we expected that as tactile expectation increases rapidly during the course of the motion of the visual stimulus, the outcome RT curves would mask the multisensory contribution of PPS. When the tactile expectation remains constant during the motion, the PPS-related spatially selective multisensory processes become apparent. The behavioural results on human experiments followed the pattern predicted by the simulation. That is, rapidly changing levels of tactile expectation, caused by dynamic visual stimuli, masks the outcome of the multisensory processes within peripersonal space. This indicates that both PPS-related multisensory interactions and tactile expectations play an important role in anticipating and responding to interactions with the body.

Location estimation of approaching objects is modulated by the observer's inherent and momentary action capabilities.

Action capability may be one of the factors that can influence our percept of the world. A distinction can be made between momentary action capability (action capability at that particular moment) and inherent action capability (representing a stable action capability). In the current study, we investigated whether there was a biasing effect of these two forms of action capability on visual perception of location. In a virtual reality room, subjects had to stop a moving ball from hitting a pillar. On some trials, the ball disappeared automatically during its motion. Subjects had to estimate the location of the ball's disappearance in these trials. We expected that if action is necessary but action capability (inherent or momentary) is limiting performance, the location of approaching objects with respect to the observer is underestimated. By judging the objects to be nearer than they really are, the need to select and execute the appropriate action increases, thereby facilitating quick action (Cole et al. in Psychol Sci 24(1):34-40, 2013. doi: 10.1177/0956797612446953 ). As a manipulation of inherent action capability in a virtual environment, two groups of participants (video game players vs. non-video game players) were entered into the study (high and low action capability). Momentary action capability was manipulated by using two difficulty levels in the experiment (Easy vs. Difficult). Results indicated that inherent and momentary action capabilities interacted together to influence online location judgments: Non-players underestimated locations when the task was Difficult. Taken together, our data suggest that both inherent and momentary action capabilities influence location judgments.

Abnormal interhemispheric connectivity in male psychopathic offenders.

BACKGROUND: Psychopathic offenders inevitably violate interpersonal norms and frequently resort to aggressive and criminal behaviour. The affective and cognitive deficits underlying these behaviours have been linked to abnormalities in functional interhemispheric connectivity. However, direct neurophysiological evidence for dysfunctional connectivity in psychopathic offenders is lacking. METHODS: We used transcranial magnetic stimulation combined with electroencephalography to examine interhemispheric connectivity in the dorsolateral and motor cortex in a sample of psychopathic offenders and healthy controls. We also measured intracortical inhibition and facilitation over the left and right motor cortex to investigate the effects of local cortical processes on interhemispheric connectivity. RESULTS: We enrolled 17 psychopathic offenders and 14 controls in our study. Global abnormalities in right to left functional connectivity were observed in psychopathic offenders compared with controls. Furthermore, in contrast to controls, psychopathic offenders showed increased intracortical inhibition in the right, but not the left, hemisphere. LIMITATIONS: The relatively small sample size limited the sensitivity to show that the abnormalities in interhemispheric connectivity were specifically related to the dorsolateral prefrontal cortex in psychopathic offenders. CONCLUSION: To our knowledge, this study provides the first neurophysiological evidence for abnormal interhemispheric connectivity in psychopathic offenders and may further our understanding of the disruptive antisocial behaviour of these offenders.

Coalescence of dominance motivation and responses to facial anger in resting-state and event-related electrophysiology.

People vary in their proneness to dominate as a function of their motivation to fulfill their need for reward and social status. Recent research suggests that in humans dominant individuals respond vigilantly to angry faces, whereas non-dominant individuals rapidly signal submission. Dominance motivation has been suggested to reside in asymmetrical patterns of cortical and subcortical processing. The ratio between δ and ß band oscillations has been proposed as a proxy for this asymmetry, which we here aimed to map onto individual patterns of the event-related potentials (N170) as well as behavioral responses to facial anger in the context of dominance motivation. Results show that dominance motivation indeed predicts increased δ in the δ/ß asymmetry; a pattern that further translates into behavioral vigilance as well as attenuation of the event-related response to angry faces. The present data are interpreted to suggest that dominance motivation is related to increased subcortical and decreased cortical processing, and that this translates into increased vigilance in dominance challenges. This motivational state is further characterized by less detailed processing of facial information as reflected in the attenuation of N170 amplitude.

Fairness modulates non-conscious facial mimicry in women.

In societies with high cooperation demands, implicit consensus on social norms enables successful human coexistence. Mimicking other people's actions and emotions has been proposed as a means to synchronize behaviour, thereby enhancing affiliation. Mimicry has long been thought to be reflexive, but it has recently been suggested that mimicry might also be motivationally driven. Here, we show during an economic bargaining game that automatic happy mimicry of those making unfair offers disappears. After the bargaining game, when the proposers have acquired either a fair or unfair reputation, we observe increased angry mimicry of proposers with an unfair reputation and decreased angry mimicry of fair proposers. These findings provide direct empirical evidence that non-conscious mimicry is modulated by fairness. We interpret the present results as reflecting that facial mimicry in women functions conditionally, dependent on situational demands.

Exploring the role of motor and non-motor predictive mechanisms in sensory attenuation: Perceptual and neurophysiological findings.

Sounds that result from our own actions are perceptually and neurophysiologically attenuated compared to sounds with an external origin. This sensory attenuation phenomenon is commonly attributed to prediction processes implicated in motor control. However, accumulating evidence suggests that attenuation effects can also result from prediction processes beyond the motor domain. The aim of the present study was two-fold. First, we attempted to replicate the role of identity-specific motor predictions in sensory attenuation. Second, we set out to examine whether attenuation effects can be observed when tones cannot be predicted from preceding actions, but only from the non-motor cues accompanying them. Participants completed a two-alternative forced choice task on the loudness of tones whose pitch was congruent or incongruent with previously learned key-tone or cue-tone associations. No convincing evidence was observed for identity predictions on a perceptual level nor on a neurophysiological level. However, exploratory analyses revealed that attenuation was more pronounced for participants who first learned to rely on motor (instead of non-motor predictions). Together, these findings suggest that the role of motor identity predictions in sensory attenuation might have to be reconsidered.

A neuroendocrine account of facial mimicry and its dynamic modulation.

Facial expressions are considered central in conveying information about one's emotional state. During social encounters, facial expressions of another individual are often automatically imitated by the observer, a process referred to as 'facial mimicry'. This process is assumed to facilitate prosocial behaviour and is thought to rely on the mirror neuron system, known for its involvement in both observation and execution of motor actions. However, recent studies have revealed mimicry to be a more dynamic process than previously conceptualized, leaving mere perception-action coupling insufficient to explain its behavioural flexibility. In the current review, we describe the consequences of these findings for the theoretical conceptualization of facial mimicry, and present a novel neuroendocrine model for the dynamic modulation of facial mimicry. Our model can guide research on the communicative function of facial expressions and can provide insight into the position of facial mimicry in theoretical models of empathy and social interaction.

Social Context Modulates Facial Imitation of Children's Emotional Expressions.

Children use emotional facial expressions of others for guiding their behavior, a process which is important to a child's social-emotional development. Earlier studies on facial interaction demonstrate that imitation of emotional expressions of others is automatic, yet can be dynamically modulated depending on contextual information. Considering the value of emotional expressions for children especially, we tested whether and to what extent information about children's temperament and domestic situation alters mimicry of their emotional expressions. Results show that angry expressions of children displaying negative behavior resulted in stronger imitation, which may serve as a corrective signal. Sad facial expressions resulted in stronger imitation towards those behaving positively but only when exposed to a difficult domestic situation, indicating increased empathy towards these children. These findings shed new light on the dynamic implicit communicative processes that shape interaction with children of different social-emotional backgrounds.

Testosterone reduces functional connectivity during the 'Reading the Mind in the Eyes' Test.

Women on average outperform men in cognitive-empathic abilities, such as the capacity to infer motives from the bodily cues of others, which is vital for effective social interaction. The steroid hormone testosterone is thought to play a role in this sexual dimorphism. Strikingly, a previous study shows that a single administration of testosterone in women impairs performance on the 'Reading the Mind in Eyes' Test (RMET), a task in which emotions have to be inferred from the eye-region of a face. This effect was mediated by the 2D:4D ratio, the ratio between the length of the index and ring finger, a proxy for fetal testosterone. Research in typical individuals, in individuals with autism spectrum conditions (ASC), and in individuals with brain lesions has established that performance on the RMET depends on the left inferior frontal gyrus (IFG). Using functional magnetic resonance imaging (fMRI), we found that a single administration of testosterone in 16 young women significantly altered connectivity of the left IFG with the anterior cingulate cortex (ACC) and the supplementary motor area (SMA) during RMET performance, independent of 2D:4D ratio. This IFG-ACC-SMA network underlies the integration and selection of sensory information, and for action preparation during cognitive empathic behavior. Our findings thus reveal a neural mechanism by which testosterone can impair emotion-recognition ability, and may link to the symptomatology of ASC, in which the same neural network is implicated.

Visuo-tactile interactions are dependent on the predictive value of the visual stimulus.

In this study we aimed to explore the predictive link between visual stimuli moving towards the body and the tactile consequences that follow. More specifically, we tested if information derived from an approaching visual stimulus in the region directly surrounding the body (the peripersonal space) could be used to make judgments about the location and time of impending tactile contact. We used moving arm stimuli, displayed on a computer screen, which appeared to travel either towards the face (middle of the left/right cheek) or slightly away from the subject's face. This stimulus was followed by tactile stimulation of the left/right cheek. The time lag between the visual stimulus and tactile stimulation was also manipulated to simulate tactile contact at a time that was either consistent or inconsistent with the speed of the approaching hand. Reaction time information indicated that faster responses were produced when the arm moved towards the hemispace in which the tactile stimulation was delivered and was insensitive to whether the arm was moving towards the cheek or slightly away from the cheek. Furthermore, response times were fastest when the tactile stimulation arrived at the moment that was consistent with the speed of the moving arm. The effects disappeared when the arm appeared to be retracting from the subject's face. These results suggest the existence of a predictive mechanism that exploits the visual information derived from objects moving towards the body for making judgments about the time and location of impending tactile contact.

Cortical information flow during inferences of agency.

Building on the recent finding that agency experiences do not merely rely on sensorimotor information but also on cognitive cues, this exploratory study uses electroencephalographic recordings to examine functional connectivity during agency inference processing in a setting where action and outcome are independent. Participants completed a computerized task in which they pressed a button followed by one of two color words (red or blue) and rated their experienced agency over producing the color. Before executing the action, a matching or mismatching color word was pre-activated by explicitly instructing participants to produce the color (goal condition) or by briefly presenting the color word (prime condition). In both conditions, experienced agency was higher in matching vs. mismatching trials. Furthermore, increased electroencephalography (EEG)-based connectivity strength was observed between parietal and frontal nodes and within the (pre)frontal cortex when color-outcomes matched with goals and participants reported high agency. This pattern of increased connectivity was not identified in trials where outcomes were pre-activated through primes. These results suggest that different connections are involved in the experience and in the loss of agency, as well as in inferences of agency resulting from different types of pre-activation. Moreover, the findings provide novel support for the involvement of a fronto-parietal network in agency inferences.

Disrupted functional brain networks in autistic toddlers.

Communication and integration of information between brain regions plays a key role in healthy brain function. Conversely, disruption in brain communication may lead to cognitive and behavioral problems. Autism is a neurodevelopmental disorder that is characterized by impaired social interactions and aberrant basic information processing. Aberrant brain connectivity patterns have indeed been hypothesized to be a key neural underpinning of autism. In this study, graph analytical tools are used to explore the possible deviant functional brain network organization in autism at a very early stage of brain development. Electroencephalography (EEG) recordings in 12 toddlers with autism (mean age 3.5 years) and 19 control subjects were used to assess interregional functional brain connectivity, with functional brain networks constructed at the level of temporal synchronization between brain regions underlying the EEG electrodes. Children with autism showed a significantly increased normalized path length and reduced normalized clustering, suggesting a reduced global communication capacity already during early brain development. In addition, whole brain connectivity was found to be significantly reduced in these young patients suggesting an overall under-connectivity of functional brain networks in autism. Our findings support the hypothesis of abnormal neural communication in autism, with deviating effects already present at the early stages of brain development.

Asymmetrical frontal resting-state beta oscillations predict trait aggressive tendencies and behavioral inhibition.

Asymmetrical patterns of frontal cortical activity have been implicated in the development and expression of aggressive behavior. Along with individual motivational tendencies, the ability to restrain one's impulses might be a factor in aggressive behavior. Recently, a role for the inhibitory cortical beta rhythm was suggested. The present study investigated whether individual differences in resting state asymmetries in the beta frequency band were associated with trait aggression and behavioral inhibition. In addition, the selective contributions of the prefrontal and motor cortex areas to these associations were examined. Results showed that relative dominant right frontal beta frequency activity was associated with both heightened trait aggression, especially hostility, and reduced response inhibition. Moreover, asymmetries over the anterior electrode locations proved to be related most closely to trait aggression, while asymmetries over the central electrode locations were associated with response inhibition. Together these findings show that right-dominant frontal beta activity is positively associated with aggressive tendencies and reduced behavioral inhibition.

Corticospinal state variability and hemispheric asymmetries in motivational tendencies.

This transcranial magnetic stimulation (TMS) study examined interrelations between asymmetrical hemispheric differences in the degree of variability of corticospinal excitability levels and motivational tendencies. The relative standard deviation in motor evoked potentials (MEP) to single pulse TMS over the left and right primary motor cortex, and approach- and avoidance-related motivational tendencies were investigated in sixty right-handed healthy volunteers. Results showed that subjects exhibited significantly higher state variability in the left as compared to the right frontal cortex and subjects displayed a dominant pattern of approach versus avoidance related motivational tendencies. Differences in left-right corticospinal state variability and approach-avoidance related motivation were significantly correlated and are consistent with the frontal lateralization model of motivational direction. This study demonstrates that MEP variability may provide an additional means for studying non-stationary properties of corticospinal excitability in relation to hemispheric asymmetries and motivational tendencies.

Alcohol breaks down interhemispheric inhibition in females but not in males: alcohol and frontal connectivity.

INTRODUCTION: Alcohol has renowned behavioral disinhibitory properties which are suggested to involve reductions in frontal lobe functioning as a result of diminished interhemispheric connectivity. METHODS: To examine sex differences in frontal interhemispheric connectivity in response to alcohol, 12 female and ten male healthy volunteers received a single administration of 0.5 per thousand alcohol in a placebo-controlled counterbalanced crossover design. Paired-pulse transcranial magnetic stimulation was applied to measure transcallosal inhibition (TCI) between the left and right primary motor cortex (M1). RESULTS: Results showed significant reductions in TCI after alcohol administration in female participants exclusively. DISCUSSION: These findings provide the first evidence that moderate doses of alcohol differentially affect frontal interhemispheric connectivity in males and females. The present data may shed new light on the physiological mechanisms underlying sex differences in the susceptibility to alcohol.

Inside the wire: aggression and functional interhemispheric connectivity in the human brain.

An aggressive personality style has been proposed to arise from a cortical asymmetry between the left and right frontal hemispheres. In the present transcranial magnetic stimulation (TMS) study, evidence was sought for a link between an aggressive personality style and functional interhemispheric connectivity between the left and right frontal cortices. Functional interhemispheric connectivity was measured by determining transcallosal inhibition (TCI) using TMS in 20 healthy right-handed volunteers, who were given the Buss-Perry Aggression Questionnaire (AQ) and a selective attention task. Analyses showed higher levels of left-to-right TCI significantly correlated with higher AQ scores. Furthermore, increased left-to-right together with reduced right-to-left TCI was associated with a stronger attentional bias for angry faces. This is the first study to provide a biological mechanism underlying the asymmetry between left and right frontal cortex activity in human aggression. We conclude that an aggressive personality style and selective attention to angry faces are positively correlated with functional interhemispheric connectivity.

Fearful faces selectively increase corticospinal motor tract excitability: a transcranial magnetic stimulation study.

Fearful facial expressions are danger signals that rapidly trigger a cascade of neurobiological processes defensibly associated with action preparation. However, direct evidence for the activating effects of fearful facial expressions on the motor system is absent. The current transcranial magnetic stimulation (TMS) study investigated whether fearful facial expressions selectively increase corticospinal motor tract (CST) excitability. Focal TMS was applied over the left primary motor cortex during the exposure of fearful, happy, and neutral facial expressions in 12 healthy right-handed volunteers. Changes in CST excitability using the motor evoked potential (MEP) were recorded. Results showed significant selective increases in MEP to fearful facial expressions. These findings provide the first direct evidence for selective increases in CST excitability to threat and contribute to evolutionary views on emotion and action preparedness.